The depot was designed in the 1960s, to service electric locomotive classes AL1 to AL6 (TOPS classes 81 to 86) and subsequently class 87s, and consists of six parallel shed roads (each holding four locomotives inside the shed) and several arrivals and departure sidings externally. There is also a road that runs round to the north of the shed and this provides access to the fuel siding, (which for many years was used only for the occasional fueling of diesel shunters), and also to the DC lines of Willesden Junction Low Level station, which is used to move multiple units from the shed onto the North London Line after servicing.

The arrival and departure sidings contain two connections to the West Coast main line onto the up slow. At the east end of the depot, there is a trailing crossover to permit access onto the down slow when coming off depot.

These include offices, a workshop and reasonably large stores. The workshop contains high quality facilities for pantograph overhaul, tap-changer overhaul and brake equipment test and servicing.

In more recent years, especially since the loss of AC electric locomotives, the fuel siding was promoted to other train operators as a facility at Willesden and a means to generate some revenue, this meant for instance that Gospel Oak to Barking Line DMUs did not need to travel to Bletchley TMD and back each night for 'A' examinations and fuelling which could instead be carried out at Willesden.